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Am Fam Physician. 2001;64(11):1892-1896

Although many maternal risk factors have been identified as indicators of poor pregnancy outcomes such as small-for-gestational-age (SGA) infants, the magnitude of these risks has not been well quantified, and little is known about the ways multiple risk factors interact with one another. Ahluwalia and colleagues studied data on SGA infants born in 13 states during 1997 to clarify the magnitude of individual and combined maternal risk factors.

The authors used data from the on-going national Pregnancy Risk Assessment Monitoring System that surveys mothers after birth and links these data to information about the pregnancy, birth and infant. In selecting states with high rates of survey completion, the researchers considered more than 19,000 births. The survey included questions about demographics, family, financial and personal information, maternal lifestyle issues such as stress, working patterns, alcohol, tobacco and drug use, and information on maternal health and pregnancy issues. Information on infants was primarily obtained from the birth certificates.

Most mothers were 20 to 34 years of age, married and multiparous, and had completed at least a high-school education. Approximately 77 percent were white and 19 percent black. Almost 40 percent were enrolled in Medicaid programs. As shown in the accompanying table, 45 percent of the pregnancies were unintended, 14 percent of the mothers smoked and 23 percent entered prenatal care after the first trimester or had no prenatal care. Levels of trauma and financial or emotional stress were significant.

Overall, 3.2 percent of infants were SGA at birth. The most significant individual risk factor was smoking, followed by low weight gain during pregnancy, little or no prenatal care, and traumatic stress. Only 10 percent of mothers had no risk factors, and many women had multiple risk factors. The percentage of SGA births was directly associated with the number of risks, rising from 1.6 percent for no risk factors to 6.4 percent for six or more risk factors.

Lifestyle and psychosocial characteristicsnPercentageStandard errorCrude OR of delivering an SGA infant (95% CI)
Maternal smoking
Yes3,00213.70.53.27 (2.45, 4.36)
No15,55586.30.5Reference
Maternal alcohol use
Yes9525.90.31.03 (0.71, 1.50)
No18,00994.10.3Reference
Weight gain for BMI*
<Recommended6,91330.50.61.96 (1.48, 2.60)
Amount recommended5,01832.10.6Reference
>Recommended5,66337.40.60.72 (0.54–0.96)
Entry into prenatal care
First trimester14,31177.40.5Reference
>First trimester or none4,65122.70.51.55 (1.17, 2.05)
Pregnancy status
Unintended8,07644.50.61.25 (0.99, 1.58)
Intended9,77955.50.6Reference
Experienced physical violence during pregnancy
Yes9504.50.31.16 (0.77, 1.76)
No18,09795.50.3Reference
Experienced partner-associated stress
Yes7,66638.20.61.19 (0.96, 1.47)
No11,48461.80.6Reference
Experienced emotional stress
Yes7,06435.60.61.06 (0.84, 1.32)
No12,10064.40.6Reference
Experienced traumatic stress
Yes4,60522.50.51.66 (1.27, 2.17)
No14,54177.50.5Reference
Experienced financial stress
Yes11,14957.20.61.11 (0.88, 1.41)
No8,01942.80.6Reference

The authors conclude that a high percentage of pregnant mothers have multiple risk factors and that delivery of an SGA infant is directly associated with the number of those risk factors. They urge health care providers to be alert to risky behaviors and other factors in pregnant women that could place the infant at risk.

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